Presently available imaging diagnostic apparatus for capturing fluoroscopic images of patients include CT (Computed Tomography) scanners, MRI (Magnetic Resonance Imaging) apparatus, PET (Positron Emission Tomography) apparatus, ultrasonic diagnostic apparatus, angiography apparatus, and MRA (MR Angiography) apparatus.
When such imaging diagnostic apparatus are used to capture a fluoroscopic image of a patient, it is occasionally practiced to inject a liquid such as a contrast media or a saline solution into the patient. A liquid injector for automatically injecting a liquid into a patient has been commercially available. Such a liquid injector has a main injector body on which a liquid syringe is removably mounted.
The liquid syringe has a hollow cylinder member filled with a liquid and a cylindrical piston member slidably inserted in the cylinder member. Generally, the cylinder member has an annular cylinder flange disposed on the outer circumferential edge of the rear end thereof, and the piston member has an annular piston flange disposed on the outer circumferential edge of the rear end thereof.
When the liquid injector is in use, the cylinder member of the liquid syringe which is filled with the liquid is connected to the patient by an extension tube, and the liquid syringe is mounted on the main injector body. In general liquid injectors, the main injector body has a concave defined in its upper surface complementary in shape to the cylinder member of the liquid syringe and its cylinder flange. Therefore, the liquid syringe is held on the main injector body when the cylinder member and the cylinder flange are placed in the concave.
The liquid injector also has a piston actuating mechanism for holding the piston flange independently of the cylinder member and sliding the piston member into and out of the cylinder member. When the piston member is pushed into the cylinder member, the liquid in the cylinder member can be injected into the patient. When the piston member is pulled out of the cylinder member, the cylinder member can draw the liquid from a liquid container.
Generally, in order to allow the liquid injector to hold various types of liquid syringes having various shapes, the concave defined in the upper surface of the main injector body is shaped to be able to receive the cylinder member of the liquid syringe having the maximum size. Liquid syringes having sizes other than the maximum size are combined with respective dedicated cylinder adapters and placed in the concave in the main injector body.
Cylinder adapters generally have concaves defined in their upper surfaces complementary in shape to the cylinder members of the liquid syringes and their cylinder flanges as the main injector body does. The cylinder members of the liquid syringes and their cylinder flanges are held in the concaves in the cylinder adapters. The cylinder adapters have lower surfaces whose outer profiles are similar to the outer profile of the cylinder member of the liquid syringe having the maximum size and the cylinder flange thereof, and are placed in the concave in the main injector body.
Liquid injectors constructed as described above have been invented by the inventor of the present invention and filed for patent (see, for example, Patent documents 1 and 2 shown below):
List of References
Patent document 1: Japanese laid-open patent publication No. 2002-11096.
Patent document 2: Japanese laid-open patent publication No. 2002-102343.
The above liquid injectors hold a liquid syringe when the cylinder member is directly placed in the concave in the main injector body or when the cylinder adapter with the cylinder member mounted in its concave is placed in the concave in the main injector body.
However, the liquid syringe may not be mounted suitably on the liquid injector, for example when the liquid syringe mounted on the liquid injector falls off during the injection operation. The operator needs to check appropriately the liquid syringe suitably mounted on the liquid injector to prevent the fall, which is difficult to achieve in reality.